1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing thread-sewn book blocks from a stack of flat sequentially juxtaposed signatures which are sewn together with a double-stranded binding thread penetrating the folds of the signature from the outside and extending along the inside edge of the folds and being pulled out of the folds at an exit point, with the help of parallel stitched seams oriented at right angles to the folds, wherein with each of the stitched seams there is associated a first sewing needle which penetrates a fold with the binding thread from the outside, and a second sewing needle which pulls the binding thread out of the fold at the exit point, wherein there are provided means for joining the binding thread which is guided inseparably in the first sewing needle, with the second sewing needle inside a spread-apart signature.
2. Description of the Related Art
A method of this type is described in EP - A - 0 295 220, wherein the double-stranded binding thread is transferred between the first to the second sewing needle through a thread carrier shuttling translationally back and forth between the two sewing needles.
This process is executed using exclusively mechanical means which are not only expensive and prone to wear, but also require a considerable effort in order to attain the proper adjustment.
These disadvantages led to the object of the present invention, namely to provide a simple method of the type described above for reducing the effort required to transfer the binding thread between the cooperating sewing needles during a sewing operation when mechanical parts are employed, and the wear associated therewith.